The invention relates to a device for producing a bead on the circumference of a hollow cylinder and is intended to include the production of a bead in general and also the production of a contraction (with or without flange) or a flange at the end of a hollow cylinder.
In known devices of this type (DT-PS 750 476, DT-OS 22 18 396) the internal and the external tool are in each case constructed functionally in one piece. This means that in the known devices, as the production of the bead progresses, the area of the hollow cylinder to be beaded is forced inward without support by the internal tool, whereas the area of the hollow cylinder adjoining the area to be beaded remains without support by the external tool and consequently may be forced to bulge outwards. These two circumstances may, either singly or more particularly taken together, lead to unwanted deformations of the hollow cylinder, in particular to the development of wrinkles and bulges.
The problem of the invention is to obviate the risk of the occurrence of these unwanted deformations, or at least to moderate this risk substantially and thereby to obtain an improvement in the quality of the beaded hollow cylinder.
This problem is solved in a device according to the present invention. An advantageous effect as achieved by a preferred embodiment resides in the fact that as the production of the bead proceeds, the inner ring supports the area to be beaded from within, while a holding-down ring supports the adjoining area from the outside. In this arrangement the radial adjustments of the holding-down ring relative to the outer ring and of the inner ring relative to the supporting mandrel, which are correspondingly necessary for this purpose, can be derived directly, by way of suitable adjusting means, from the drive for the device.
A relatively simple construction for the device according to the present invention results if the radial adjustments are derived only indirectly from the drive for the device. This can be through the fact that radially acting springs urge the inner ring and the supporting mandrel on the one hand and the outer ring and the hold-down ring on the other hand into coaxial positions relative to one another. Then, with a reduced radial distance of the outer ring from the axis of the supporting mandrel as the production of the bead progresses, under the pressure of the outer ring acting radially from the outside, the inner ring yields radially inwards relative to the supporting mandrel, while under the pressure of the supporting mandrel acting radially from the inside, the hold-down ring yields radially outwards relative to the outer ring.
In a preferred embodiment of the device according to the present invention wherein the external tool can be adjusted radially inwards relative to the internal tool in opposition to the force of a spring acting radially outwards, as known per se (DT-PS 750 476), that is to say there is derived directly from the drive for the device only a radially inwardly directed adjustment of the external tool relative to the internal tool, a construction wherein the spring arrangements include springs which are disposed in the axial direction and wherein means for deflecting their forces are formed by pairs of tapered ring surfaces surrounding the axis of the supporting mandrel gives a particularly simple and compact arrangement.
The radial adjustments which have been described may also be effected in opposition to the forces of suitably disposed cylinder-piston units, while it is also possible according to another embodiment of the invention to obtain a particularly simple and compact construction if the cylinder-piston units are disposed axially and the forces are diverted into the radial direction by way of pairs of tapered rings surrounding the axis of the supporting mandrel.
Should sections of the hollow cylinder adjoin the area of the hollow cylinder to be beaded in both axial directions, that is to say a bead in the narrower sense is to be produced, the supporting mandrel and the holding-down ring may, according to the invention, have sections extending in both axial directions from the inner ring or the outer ring.
The device according to the invention can be applied both in the single arrangement known per se (DT-PS 750 476) and also in the multiple arrangement known per se (DT-OS 22 18 396) with a plurality of internal and external tools disposed radially on a tool carrier with rotary drive, in which arrangement, in the latter case, it is convenient if the controlled radial adjustability of the external tools relative to the internal tools is derived from the drive by means of a controlling cam which partially surrounds the tool carrier.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a single embodiment in accordance with the present invention.